The present application relates to semiconductor devices, and more particularly to power diodes and switching modules.
Note that the points discussed below may reflect the hindsight gained from the disclosed inventions, and are not necessarily admitted to be prior art.
Conventionally, diodes provide charge-blocking capabilities, but suffer from the reverse recovery charge problem. That is, when a conventional diode is active and conducting current (in the appropriate direction), turn-off produces an undesirably-large reverse current to equilibrize the induced voltage difference, which can negatively impact performance. Conventionally, diodes deal with this problem by minimizing minority carrier lifetimes in the diode.
The present application teaches, among other innovations, diodes with an added control terminal, and methods of operating controllable diodes to reduce recovery charge. Most preferable a control terminal is added on the side of a diode closest to its p-n junction, and is separated from the junction region by an insulated trench. In preferred operation methods, the control terminal is driven to reduce the minority carrier density before the zero-crossing of current.
In one class of embodiments, the control terminal is driven toward a voltage which is not within the range of the anode and cathode voltages.
For example, in one class of embodiments, the semiconductor die is p-type, and the control terminal is located on the same surface with the cathode terminal. In a modification of this embodiment, the control terminal is optionally driven to a voltage which is slightly more negative than the cathode terminal.
In another class of embodiments, the semiconductor die is n-type, and the control terminal is located on the same surface with the anode terminal. In a modification of this embodiment, the control terminal is optionally driven to a voltage which is slightly more positive than the anode terminal.